When a person suffers a stroke, one of the resulting physical impairments is wrist spasticity, which causes excessive wrist stiffness and resistance to stretch, known as “tone.” Studies suggest that this increase in stiffness, or tone, may be due to changes in the wrist flexor and extensor muscles, which result in an increased torque demand to achieve wrist movement.
While devices have been developed that provide assistive force or torque to the wrist in flexion or extension to assist with wrist movement, such devices only provide assistance in one of these directions. Moreover, this assistance decreases as the angular rotation of the wrist increases, which is the opposite of what is needed given that rotation becomes more difficult as the angle of rotation increases. In view of this, it can be appreciated that it would be desirable to have a device that mitigates the intrinsic stiffness of stroke victim wrists and therefore provides assistance to the individual in bending the wrist in both flexion and extension, as well as holding a desired angular position.